The objective of this proposed R21 exploratory research is to explore the intersection of minority stress for adolescents who identify as sexual (lesbian, gay, bisexual) and racial/ethnic minority and to develop and validate a sexual minority adolescent stress instrument (SMASI). The production of a valid measure of minority stress for this population will have a significant public health impact by allowing for more precise assessment of the relationship between minority stress experiences (social processes) and negative mental and behavioral health outcomes in this higher risk population. Adapted from effective methods used in similar NIH research with ethnic minority adolescents, the proposed research will result in the development of a valid measure of minority stress that can be used to inform clinical assessment and the development of effective targeted behavioral health interventions. The objectives will be met through two specific aims, including: a) Create a preliminary Sexual Minority Adolescent Stress Inventory (SMASI) through a modified Delphi process with an expert panel; and b) Refine the instrument and assess its reliability and preliminary criterion validity in a cross- sectional study of racially and ethnically diverse sexua minority adolescents (N=410). This study will apply a mixed method, multi-phase design to the development of the SMASI. During the first year, a preliminary SMASI will be developed using a modified Delphi process with an interdisciplinary subject matter expert panel, followed by youth cognitive interviews (n=20) to ensure comprehensibility of the draft measure. Phase II will occur in the second year of the study, when a racially and ethnically diverse range of SMA (n=410) will be recruited using respondent driven sampling to complete the draft measure. Analysis of phase II will focus on establishing reliability and preliminary criterion validity, and the production ofa final SMASI. Upon completion of this R21, a multi-year study will be conducted to examine the longitudinal relationship between minority stress experiences and mental and behavioral outcomes in a large sample of racially and ethnically diverse youth.